Device for eliminating yarn slack in knitting machines

ABSTRACT

A device to be used in knitting machines for eliminating slack in yarn. The yarn travels from a suitable source of supply to a part of the machine where the yarn is acted upon. In the path of travel of the yarn is located a hollow cylinder having opposed open ends, and the yarn extends into the cylinder at one of the open ends thereof. A piston is freely movable within the cylinder and carries an eye through which the yarn passes before travelling out of the cylinder through the same end at which the yarn enters the cylinder. An evacuating structure communicates with the interior of the cylinder at the side of the piston which is directed away from the yarn guiding eye, so as to create in this part of the cylinder a lesser pressure tending to draw the piston further into the cylinder so as to eliminate any slack in the yarn.

United States Patent 1 1 3,601,332

[72] Inventors Alois Kubelka; 3,464,452 9/1969 Brouwer et a]. 242/147 R granltliselk Svklaohoda, both of 33110, FOREIGN PATENTS 347,210 4/1931 Great Britain 242/147 836392 489 709 1 1954 It 1 242/147 [22] Filed June251969 ay [45] Patented Aug. 24, 1971 Primary ExaminerAllen N. Knowles [73] Assignee Vyzkul'nny ustav pletarsky An0rneyArthur O. Klein Brno, Czechoslovakia [32] Priority June 27, 1968 [33] Czechoslovakia [31] 4723-68 ABSTRACT: A device to be used in knitting machines for 54 DEVICE FOR ELIMINATING YARN SLACKIN eliminating slack in yarn. The yarn travels from a suitable KNITTING MACHINES source of supply to a part of the machine where the yarn is 9 Claims 3 Drawing Flax acted upon. in the path of travel of the yarn is located a hollow 2 Us C 1 cylinder having opposed open ends, and the yarn extends into 242/147 A, the cylinder at one of the open ends thereof A piste is freely 242/154 movable within the cylinder and carries an eye through which [51] Int. Cl B65h 59/00 the yam passes b f travelling out f the cylinder through [50] Field of Search 226/196, the Same end at which the yam enters the cy]inder An 9144, 19.1;66/146i242/147 147A evacuating structure communicates with the interior of the 1561 Rem-MM 51:32:;3311335325;1322;129:215,32221111135512: UNITED STATES PATENTS a lesser pressure tending to draw the piston further into the 3,080,154 3/1963 Tanner 222/392 X cylinder so as to eliminate any slack in the yarn.

l i, 1 j i 5 1' l I l PATENTED AUB24 l97| NVENTORSZ Aloi: KUBELKA BY; Franh sek SVOBODA Mam DEVICE FOR ELIMINATING YARN SLACK IN KNITTING MACHINES BACKGROUND OF THE INVENTION 7 The present invention relates to knitting machines.

- In particular, the present invention relates to devices to be used with knitting machines for preventing the formation of any slack in yarn which travels to the knitting machine from a suitable yarn supply. The invention is particularly applicable to devices for tensioning yarn on straight-bar and circular weft-knitting machines, particularly circular knitting machines of relatively small diameter.

Straight-bar knitting machines are generally provided with a reciprocating carriage, and the yarn which is worked by the machine necessarily becomes slack at the dead center locations of carriage travel. Thus, after a course is knitted, the carriage must travel to the dead center location, irrespective of the particular fabric width, so that the yarn guides which are carried by the carriage move also to their dead center locations situated beyond the fabric selvedges. During movement from the fabric selvedge to the respective dead center location, the yarn guide continues to draw the supplied yarn. The result is an undesirable formation of slack in the yarn when the beginning of the knitting of the next course takes place. Such slack in the yarn must be compensated in order to provide for the first needles which form the new course yarn which is properly tensioned, so as to achieve a knitted fabric where the initial loops are not looser than the remaining loops of the particular course.

In order to solve this problem, known machines use special tensioning devices, called tension trappers, in the form of a rockable lever having an eyelet at one end and acted upon by a spring which opposes the pull of the yarn.

-During reciprocatory knitting on small-diameter circular knitting machines, slack is formed in the yarn in a similar. manner, except that in this case the yarn guide is stationary and the needle cylinder rotates. The tensioning device of such a machine operates on the same principle as on the straightbar machine.

These known tensioning devices have a number of disadvantages. The springs thereof must be prestressed to a considerable degree, particularly if the narrowing range during the knitting operations requires a long swinging movement for the tension trapper. This prestress increases the yarn tension and results in impacts in the yarnduring tension trapper movements. As a result the yarn is strained excessively, with an unavoidably increased frequency of yarn breakage. Inasmuch as the spring characteristics are variable relative to the length of the tension trapper stroke, the density of the lateral yarn loops varies also. As a result of these undesirable effects and as a result of The inertia of the tensioning device, the knitting speed is necessarily limited. Particularly in the case of circular knitting, the speed must be substantially reduced during reciprocatory knitting, so that the construction of the machine is rendered far more difficult.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide a construction which will avoid the above drawbacks.

In particular, it is an object of the invention to provide a construction which will avoid the above drawbacks on straight-bar as well as circular knitting machines, particularly small-diameter circular knitting machines.

Furthermore. it is an object of the invention to provide a device which is relatively simple in its construction while at the same time capable of reliably eliminating any slack in the yarn.

Also. it an object of the invention to provide a construction which is readily adjustable so that it will operate according to the characteristics of the particular yarn which is treated.

In accordance with the invention the device includes an elongated hollow cylinder having opposed open ends and a piston axially movable within the cylinder and carrying a yarn guide at an end of the piston which is directed toward one of the open ends of the cylinder. The yarn enters from a suitable supply into the cylinder through this open end thereof, and after going around the yarn guide at the piston passes out through the same end of the cylinder. An evacuating means communicates with the interior of the cylinder through the other of the open ends thereof, so that this evacuating means provides in the cylinder at the side of the piston which is directed away from the yarn a lesser pressure than the pressure prevailing in the cylinder at the side thereof which receives the yarn. As a result the piston tends to be drawn further into the cylinder thus tensioning the yarn so as to eliminate any slack which tends to form therein. The extent of vacuum is adjustable so as to provide uniform yarn tension and, consequently, uniform fabric density, even at the slelvedges. At the same time, this construction prevents undesirable excessive yarn tension and impacts, and the frequency of yarn breakage is greatly reduced.

In order to prevent the piston from turning within the cylinder the piston is provided at its exterior surface with an axial groove which receives a rod extending axially along and carried by the cylinder, this rod having an inner end which extends substantially radially with respect to the cylinder axis and is situated in the path of movement of the piston to limit the movement of the latter into the cylinder.

BRIEF DESCRIPTION OF DRAWINGS DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings, it will be seen that the device of the invention includes an elongated hollow cylinder 1 which is vertically oriented and which has opposed upper and lower open ends. The all open end is in communication, in a fluidtight manner, with a conduit 2 (FIG. 1) which in turn communicates with a vacuum-creating device 4 which may form part of a central pneumatic system for removing dust, fabric takeup, etc. Thus, conduit 2 together with the blower 4 or the like form an evacuating means for evacuating the lower region of the cylinder 1, as viewed in the drawing.

Within the cylinder 1 is a piston 5 which is freely movable within the cylinder between the opposed open ends of the latter. This piston 5 also has opposed ends, and the upper one of the ends of the piston 5 fixedly carries a yarn guide in the form of an eyelet 6. The yarn 7 is derived from any suitable supply, such as the package 15, and travels through a disk brake 10 of known construction, carried by a bracket 9, before reaching the cylinder 1. Thus, FIG. 2 shows the bracket 9 extending angularly from a side of the cylinder 1, where this bracket 9 is mounted, and carrying the disk brake 10 which acts on the yarn prior to travel of the yarn to the cylinder. The yarn 7 enters into the cylinder through the top open end thereof, goes around the yarn guide, passing through the eyelet 6, and then again moves out though the top open end of the cylinder so as to continue on itsway to theknitting structure. At its top open end the cylinder 1 fixedly carries a ring 8 made of a hard metal or ceramic which has a low coefficient of friction with respect to the yarn do that the latter will move freely into and out of the cylinder while engaging diametricall opposed parts of the ring 8. The eyelet 6 may be made of the same material as the ring 8 The piston 5 is formed at its exterior surface with an axial groove 11 which receives an elongated rod 12 which has at its top end a hook 13 extending over the ring 8 so as to rest in this way on the cylinder 1 at the top open end thereof while extending axially along the interior of the cylinder next to the wall thereof. Thus, this rod 12 will prevent rotary movement of the piston 5 within the cylinder 1. The piston 5 can slide freely along the rod 12. At its lower end the rod 12 carries a stop 14 which limits the extend of movement of the piston 5 into the interior of the cylinder 1. This stop 14 simply takes the form of an angularly bent end of the rod 12 extending radially from the remainder of the rod 12 toward the axis of the cylinder and situated in the path of downward movement of the piston 5 so as to limit this movement thereof.

The lower end portion of the rod 12 acts as a stop 14 for the piston and simultaneously for withdrawing the same from the cylinder 1 in case of thread breakage. In case of the breaking of a thread, the stop 14, by merely pulling the opposite bent end 13 of the rod 12 upwardly, will engage the lower piston face so that the piston 5 is lifted upwards so that the eyelet 6 thereon may be threaded-in again. The piston 5, resting upon the stop 14, will then be allowed to drop together with the rod 12 into the cylinder so that it again occupies the position thereof shown in FIG. 1, wherein the rod 12 is hung by its upper end 13 over the upper edge of the cylinder 1.

The structure described above operates as follows:

The yarn which travels from the supply of package 15 toward an unillustrated yarn guide of the knitting machine passes through the disk brake and over a part of the ring 8 into the cylinder 1 where the yarn first goes through the eyelet 6 and then passes out of the cylinder over an opposed part of the ring 8 to the unillustrated yarn guide of the knitting machine. The piston 5 is acted upon by the lesser pressure which prevails in the interior of the cylinder beneath the piston 5 so that the piston 5 tends to be drawn further into the cylinder in the direction of the arrow S shown in FIG. 2. On the other hand, the tension in the yarn tends to pull the piston 5 in the opposite direction S also indicated in FIG. 2. The evacuating means is adjustable by way ofa valve 3, so that the extent of vacuum prevailing in the cylinder beneath the piston 5 can be regulated. The manner in which the piston 5 is prevented from rotating by the rod 12 is clearly apparent from FIG. 3.

During movement of the yarn from the fabric selvedge toward the dead center location, the yarn guide of the knitting machine unwinds yarn 7 from the supply package 15, with this yarn, which travels from the package 15, still being out of engagement with the knitting needles. As soon as the direction of traverse is changed at the dead center location and the yarn guide starts to return to the fabric selvedge, the tension of the yarn unwound from the package drops so as to tend to create slack in the yarn. However, because of the lesser pressure acting beneath the piston 5 in the cylinder 1, the piston 5 is drawn down further into the cylinder so as to increase the yarn tension beyond the extent to which the yarn would be tensioned if slack were formed. The extent ofincrease in yarn tension at this time is such that the opposed forces acting on the piston 5 are in equilibrium. Thus, for example, the piston at this time may be at the position 1 indicated in FIG. 2.

If, subsequently, during the operation of the knitting machine the yarn tension is increased, then this tension will exceed the force of the evacuated space tending to draw the piston 5 further into the cylinder, with result that the piston 5 is raised by the yarn which is under tension to an elevation such as the position ll indicated in FIGS. 1 and 2, for example, in dotted lines. The piston will stop when the opposed forces are in equilibrium.

It is to be understood that the device of the invention is not limited to all of the details described above and shown in the drawing. For example, both the cylinder and the piston can have a triangular, rectangular, or any other polygonal cross section.

What is claimed is: l 1. In a knitting machine, a device for eliminating slack in yarn travelling from a yarn supply to a part of the machine where the yarn is acted upon, said device comprising an elongated hollow cylinder having opposed first and second ends, the first end of the cylinder being open, a piston in said cylinder, said piston being axially movable in said cylinder and also having a pair of opposed first and second ends, respectively, a yarn guide carried by said piston at said first end thereof for pulling a yarn into the said cylinder through said corresponding first end thereof, the yarn travelling around said yarn guide, and then out of said cylinder through said first open end thereof, and evacuating means communicating with the interior of the cylinder at the second end thereof for evacuating that part of said cylinder which is situated between said second end thereof and the second end of said piston, which is opposed to that end thereof which carries said yarn guide, whereby the lesser pressure provided in said cylinder between said piston and said second end of said cylinder causes said piston to act through said yarn guide on the yarn to eliminate any slack therein.

2. The combination of claim 1 and wherein said yarn guide is in the form of any eye throughwhich the yarn passes.

3. The combination of claim 1 and wherein said cylinder carries at said first open end thereof a ring of a hard material which has a low coefficient of friction with respect to the yarn entering into the cylinder at one part of said ring and moving out ofthe cylinder at an opposed part of said ring.

4. The combination of claim 1 and wherein said piston is formed at an exterior surface thereof with an axial groove, and a rod carried by said cylinder and extending through said groove of said piston to prevent rotary movement thereof in said cylinder.

5. The combination of claim 4 and wherein said rod carries between said piston and said second end ofsaid cylinder in the evacuated portion thereofa stop which is situated in the path of movement of said piston to limit the movement thereof away from said first, open end of said cylinder.

6. The combination moves out 4 and wherein said rod has an outer curved end, said outer curved end extending over said cylinder at said first end thereof for ready removal therefrom.

7. The combination of'claim 6 and wherein said cylinder is vertically oriented with said first end thereof situated at the uppermost part of said cylinder and with said rod resting on said cylinder at said first end thereof.

8. The combination of claim 5 and wherein said stop carried by said rod is in the form ofa laterally extending rod portion extending substantially radially from an axially extending part of said rod.

9. The combination of claim 1 and wherein said evacuating means includes a conduit and an adjustable valve carried by said conduit for regulating the extent of vacuum achieved by said evacuating means. 

1. In a knitting machine, a device for eliminating slack in yarn travelling from a yarn supply to a part of the machine where the yarn is acted upon, said device comprising an elongated hollow cylinder having opposed first and second ends, the first end of the cylinder being open, a piston in said cylinder, said piston being axially movable in said cylinder and also having a pair of opposed first and second ends, respectively, a yarn guide carried by said piston at said first end thereof for pulling a yarn into the said cylinder through said corresponding first end thereof, the yarn travelling around said yarn guide, and then out of said cylinder through said first open end thereof, and evacuating means communicating with the interior of the cylinder at the second end thereof for evacuating that part of said cylinder which is situated between said second end thereof and the second end of said piston, which is opposed to that end thereof which carries said yarn guide, whereby the lesser pressure provided in said cylinder between said piston and said second end of said cylinder causes said piston to act through said yarn guide on the yarn to eliminate any slack therein.
 2. The combination of claim 1 and wherein said yarn guide is in the form of any eye through which the yarn passes.
 3. The combination of claim 1 and wherein said cylinder carries at said first open end thereof a ring of a hard material which has a low coefficient of friction with respect to the yarn entering into the cylinder at one part of said ring and moving out of the cylinder at an opposed part of said ring.
 4. The combination of claim 1 and wherein said piston is formed at an exterior surface thereof with an axial groove, and a rod carried by said cylinder and extending through said groove of said piston to prevent rotary movement thereof in said cylinder.
 5. The combination of claim 4 and wherein said rod carries between said piston and said second end of said cylinder in the evacuated portion thereof a stop which is situated in the path of movement of said piston to limit the movement thereof away from said first, open end of said cylinder.
 6. The combination moves out 4 and wherein said rod has an outer curved end, said outer curved end extending over said cylinder at said first end thereof for ready removal therefrom.
 7. The combination of claim 6 and wherein said cylinder is verTically oriented with said first end thereof situated at the uppermost part of said cylinder and with said rod resting on said cylinder at said first end thereof.
 8. The combination of claim 5 and wherein said stop carried by said rod is in the form of a laterally extending rod portion extending substantially radially from an axially extending part of said rod.
 9. The combination of claim 1 and wherein said evacuating means includes a conduit and an adjustable valve carried by said conduit for regulating the extent of vacuum achieved by said evacuating means. 